Spark gap



Sept. 21,1948; J. E. GORHAM ETAL 2,449,552,

SPARK GAP Filed- Jan. 14, 1943 FIG 3 INVENTOR JOHN E. GORHAM' HAROLD A. ZAHL.

TTORNEY Patented Sept. 21 1948 SPARK GAP John E. Gorham, Spring Lake, and Harold A. Zahl, Long Branch, N. J.

Application January 14, 1943, Serial No. 472,353 14 Claims. (01. 250-38) (Granted under the act of March 3, 1883, as f j amended April 30,. 1928; 370, 0. G. 757).

' The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to usof any royalty thereon.

This invention relatesto spark gaps, and more particularly to a spark gap having repeatedly renewable electrode surfaces.

In some cases a radio transmitter and receiver may be connected to a common antenna. Pulse echo systems for locating and ranging are an important example. In such cases it may be necessary to protect the receiver during the time the transmitter is on. One means for this purpos is a spark gap having electrodes set closely together, said spark gap being connected across the transmission line near the receiver, or across transmission line stubs of appropriate length.

Fixed spark gaps sealed within a glass envelope have been used, but in some types of apparatus it has been found that thelife of such a spark gap is very short. The primary object of the present invention is to overcome the foregoing difficulty, which we do by the provision of a spark gap having repeatedly renewable electrode surfaces.

Another difficulty with spark gaps arises from sputtering of metal onto the insulation material between the electrodes. Enough metal may gather to form a continuous layer between the electrode supports, with consequent short circuit. Another object of the present invention is to prevent short eircuiting of the spark gap despite sputtering of the electrode metal.

To the accomplishment of the foregoing general objects, and other more specific objects which will hereinafter appear, our invention resides in the spark gap elements and their relation one to another, as are hereafter more particularly described in the specification. The specification i accompanied by a drawing in which:

Figure 1 is a front elevation of a spark gap embodying features of our invention;

Figure 2 is a plan view thereof;

Figure 3 shows one of the electrode brackets,

looking in the direction of the axis of the electrode;

Referring to the drawing, and more particularly to Figures 1 and 2, the complete spark gap com- Figure 4 shows the separated parts of an electure as so fardescribed the sputtered metal will prises electrodeslZ and I4 arranged end to end in coaxial relation. The gapbetween the electrodes is adjustable by means of. electrode screws I6 and I8. These are screwed through brackets 20 and 22, which in turn are secured to an insula tion base 24 by means of screws 26 and 28. The adjusting screws have integrally formed'knobs'at their outer ends to facilitate adjustment. The upper ends of the brackets 20 and 22 are preferably split, as is indicated at 30 in Figures 2'and 3, and the split halvesof the bracket may be drawn together by means of lock screws 32. a

Referring now to Figures 4, 5 and 6 of the drawing, it will be seen that the electrode screw l8 has a cylindrical bore running therethru. The electrode tip I4 is one end of a solid rod 36 of electrode material. This rod is slidably received in the hollow electrode screw l8. It will be evi dent that when the electrode surface is worn away the gap may be readjusted to proper dimension by rotation of the electrode adjusting screws. After these screws have been readjusted a number of 1 times theworn away electrodetip may be renewed by shifting the electrode rod axially until it projects therefrom by the original amount.

Suitable means may be providedto fix the posi#. tion of the electrode rod within the screw. In, the present case the end of the electrode screw is radially slotted and compressible. Specifically, there are four slots 40 (see Fig. 6), and the end of the screw is tapered at 42. A knurled lock nut 44 is threadedly received over the split end of thea djusting screw. The nut has atapered.

internal surface 46 which mates with the tapered end 42 of the adjusting screw. It will be evident that an tightening the lock nut 44, the slotted ends of the screw will be compressed inwardly and so clamped against the electrode rod.

The wearing away of the electrode tipis accompaniedby sputtering ofthe discharge metal. The sputtering metalwill adhere to and fo-rm'a coatingon any adjacent surface. With the strucaccumulate on thetop surface48 (Fig 1) of the insulation base 24. After long continued use the resulting film of sputtered material spreads: along the base and finally acts as a continuous conductor between the base portions 50 of the brackets 20 and 22. This short circuits the spark gap and so spoils the operation of a receiver connected f thereto. a a

In accordance with a feature of the present invention a disc or plate 52 is disposed betweenthe base 48 and the adjustable electrode tips I2 and 1 M. The sputter plate 52 is mounted on the upper end of a post 54, and is held in position by means of a screw 56 which passes through the disc 52, the post 54, and a nut 58.

It will be evident that because the disc 52 is substantially larger in diameter than the post 54, and because it is located relatively near the elsetrodes, the sputtered metal will be accumulated on the disc 52, and so will prevent the deposit of metal on the center part of the base 24. There is no likelihood of sputtered metal collecting on the under side of disc 52, and there is accordingly no danger of the spark gap becoming short circuited by sputtered metal.

An additional safeguard against the formation of a continuous film of sputtered metal is provided by the shape of the brackets. noted that the base portion 50 is cut away at 60 (see Fig. 1), thus providing a root or shield over the end portions of th base. Moreover, the brackets project inwardly at 6|, beneath the shutter disc 52, so. that ordinarily there will be no, sputtering of metal on the base 24.

The brackets 29. and 22 act also as clamps for clamping the spark gap to the transmission line. In the present case the transmission line is indicated by the tubing 62; This may be copper tubing, or other suitable high frequency transmission line. In Figure 7 it will be seen that the bracket isconcavely shaped at 64 to complement an oppositely curved clamp block 66, the latter being. secured to the bracket by means of a clamp screw 68. With the clamp blocks removed or. turned upwardly, the spark gap is readily applied to the-parallel tubes 62 of the transmission line,v whereupon the dla mp blocks are turned downward and: the clamp screws 68 tightened, thus. attaching the spark gap to the transmission line.

The electrode rods are preferably made of a refractory metal. such as tungsten, although molybdenum may also be used. The metal should be relatively non-oxidizable, non-volatile at high temperature, and conductive. The brackets, and electrode'adjusting screws are preferably made of brass or like highlyconductive metal. The insulation should be se'lected'for highradio frequency work. Polystyrene is a good material for this purpose.

It is believed that the (construction and operation ofour improved spark gap, as well as the advantages thereof, will be apparent from the foregoing description; It will also be apparent that'while we have shown and described our invention in a preferred form, changes and modifications may be made in the structure disclosed without departing from the spirit of the invention, as sought to be defined in the following claims.

We claim:

l. A spark gap assembly comprising an insulation base, spaced brackets mounted thereon, electrodes carried by. said brackets, a sputterplate disposedbetweensaid base and the adjacent ends ils id electrodes. and a. post support sa d sputter plateon said base, the cross section of aid. p st be ng substantia y sma e than the zqsslscction f; aid ut er p at said sputter plate ser in tcrrcve t the accumulation of a continuous layer-of: sputtered metal on said base between said brackets.

2; A. spark gap assembly comprising an insulation base, spaced brackets mounted thereon, and eleotrodeslcarried bysaid brackets, the base portion. of said brackets being so shaped or under- Itwill be.

cut as to shield said insulation base against sputtered metal.

3. A spark gap assembly comprising an insulation base, spaced brackets mounted thereon, electrodes carried by said brackets, a part of said brackets being; shaped to receive spaced tubular transmission lines, and having clamp blocks and screws associated therewith for clamping the spark gap in position on the transmission line.

4. A spark gap assembly comprising an insulation base, spaced brackets mounted thereon, electrodes carried by said brackets, a sputter plate disposed between said base and the adjacent ends of said electrodes, and a post supporting said sputter plate on said base, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets, and the base portion of said brackets being so shaped or undercut as to further shield said insulation base against sputtered metal.

5. A spark gap assembly comprising an insulation base, spaced brackets mounted thereon,

electrodes carried by said brackets, the basepor tion of said brackets being so shaped or undercut as to shield said insulation base against sputtered metal, a part of said brackets being shaped to receive spaced tubular transmission lines, and having clamp blocks and screws associated therewith for clamping the spark gap in position on the transmission line.

6. A spark gap assembly comprising an insu lawith for clamping the spark gap in position on.

the, transmission lline.

7'. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, hollow electrode screws threadedly received in said brackets, a rod of electrode material carried in each said electrodev screw and projecting from one end thereof, lock means to. fix the position of said electrode rods in each said hollow: electrode screw, said lock means including a llock nut threadedly. received on. the end of. each said electrode screw, said; andv being slotted and. so-

tapered that tightening of the lock nut squeezesthe split ends of the electrode screw against the electrode rod, a part of said. brackets being shaped to receive Spaced.v tubular transmission lines, and having clamp blocks andv screws associated therewith for clamping the spark. gap. in.

position on the transmission line.

8.. A spa k gap ss m y comprising an insuiation base, spaced brackets fixedly mounted there,- on, a hollow electrode-holder axially and adjust-- ably receivedin. each of said brackets, a rodwf elec rode material carried in said electrode holders and projecting from, one end thereof, lock means to fix the position of said electrode, rods in said hollow electrode holders, a sputter plate disposed. betweensaid base and the adj acentends d 'c trode. ro and a p for sunpcrtins salid sputter plate on said base, the cross section area of said post being substantially smaller than the area of said sputter plate, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets.

9. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, a hollow electrode holder axially and adjustably received in each of said brackets, a rod of electrode material carried in each of said electrode holders and projecting from one end thereof, lock means to fix the position of said rod in said hollow electrode holder, the base portion of said brackets being so shaped or undercut as to shield the insulation base against sputtered metal.

10. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, a hollow electrode holder axially and adjustably received in each of said brackets, a rod of electrode material carried in each of said electrode holders and projecting from one end thereof, lock means to fix the position of said rod in said hollow electrode holder, a sputter plate disposed between said base and the adjacent ends of said rods, and a post supporting said sputter plate on said base, the cross section of said post being substantially smaller than said sputter plate, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets, the base portion of said brackets being so shaped or undercut as to further shield said base against sputtered metal.

11. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, hollow electrode screws threadedly received in said brackets, lock means for locking the adjustment of said electrode screws, a rod of electrode material carried in each of said electrode screws and projecting from one end thereof, additional lock means for fixing the position of said rods in said hollow electrode screws, said additional lock means including a lock nut threadedly received on one end of each of said electrode screws, said ends being slotted and so tapered that tightening of said lock nuts squeezes said slotted ends of said electrode screws against said rods, a sputter plate disposed between said base and the adjacent ends of said rods, and a post supporting said sputter plate on said base, the cross section of said post being smaller than that of said sputter plate, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets.

12. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, hollow electrode screws threadedly received in said brackets, lock means for locking the adjustment of said electrode screws, a rod of electrode material carried in each of said electrode screws and projecting from one end of each of said screws, additional lock means for fixing the position of said rods in said hollow electrode screws, said additional lock means including a. locknut threadedly received on said ends of said electrode screws, said ends being slotted and so tapered that tightening of said lock nuts squeezes said slotted ends of said electrode screws against said rods, the base portion of said brackets being so shaped or undercut as to shield said base against sputtered metal.

13. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, hollow electrode screws threadedly received in said brackets, the ends of said brackets supporting said electrode screws being split and provided with lock screws for locking the adjustment of said electrode screws, a rod of electrode material carried in each of said electrode screws and projecting from one end of each said electrode screws, lock means for fixing the position of said rods in said hollow electrode screws, said lock means including a lock nut threadedly received on said ends of said electrode screws, said ends being slotted and tapered to mate with a tapered part of said lock nuts, whereby tightening of said lock nuts squeezes said slotted ends of said electrode screws against said electrode rods, a sputter plate disposed between saidbase and the adjacent ends of said electrode rods, and a post for supporting said sputter plate on said base, the cross section of said post being smaller than that of said sputter plate, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets, the base portion of said brackets being so shaped or undercut as to further shield said base against sputtered metal.

14. A spark gap assembly comprising an insulation base, spaced brackets fixedly mounted thereon, hollow electrode screws threadedly received in said brackets, means for locking the adjustment of said electrode screws, arod of electrode material carried in each of said electrode screws and projecting from one end of said screws, lock means to fix the position of said rods in said hollow electrode screws, said lock means including lock nuts threadedly received on said ends of said electrode screws, said ends being slotted and so tapered that tightening of said lock nuts squeezes said slotted ends of said electrode screws against said electrode rods, 2. sputter plate disposed between said base and the adjacent ends of said electrode rods, and a post for supporting said sputter plate on said base, the cross section of said post being smaller than that of said sputter plate, said sputter plate serving to prevent the accumulation of a continuous layer of sputtered metal on said base between said brackets, the base portion of said brackets being so shaped or undercut as to further shield said base against sputtered metal, a part of said brackets being shaped to receive spaced tubular transmission lines, and having clamp blocks and screws associated therewith for clamping the spark gap assembly in position on the transmission lines.

JOHN E. GORHAM. HAROLD A. ZAHL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 751,854. Hofiman Feb. 9, 1904 831,599 Browne Sept. 25, 1906 887,220 Pauling May 12, 1908 1,428,856 Parker Sept. 12, 1922 1,521,361 Davis Dec. 30, 1924 1,766,665 Meckel June 24, 1930 1,780,600 Pullwitt Nov. 4, 1930 

